High Calcia Glaze
Glaze is fired at cone 6 in an electric kiln.
The kiln is cooled slowly, at a rate of 25 deg F an hour in the temperature interval 1750 deg F to 1650 deg F, with a 1 hour hold at 1650 deg F.
dappled glaze
glaze loAlk_185_0 on a fluted cylinder diameter ~4 inches high
Composition
The bases in this glaze are predominantly CaO and Li2O, with trace quantities of K2O and Na2O.
This glaze is composed of clay, silica, spodumene and whiting, not quite a quarter of each. It has moderate alumina of .4, and silica: alumina ratio 6.3.
This is a high calcia glaze, with CaO .78.
Comment
The strong phase segregation which produced the mottled tan and white appearance is a surprise. The appearance tan markings suggests they constitute a separate non-crystalline phase.